Liquid crystal display and dimming control method thereof

Abstract

A dimming control method of a backlight unit of a liquid crystal display (LCD) device driven at a driving frequency (f) of 60 Hz or lower includes a first step of driving the backlight unit using a first dimming value, and a second step of driving the backlight unit using a second dimming value higher than the first dimming value. The first step and the second step are alternately repeated and a repetition number of the second step within one period T of a driving frequency (f) is set to satisfy a condition of “{(60/f)−1}”. Here, f is a natural number lower than 60.

What is claimed is: 
     
       1. A dimming control method of a liquid crystal display (LCD) device driven at a driving frequency (f) of 60 Hz or lower, the dimming control method comprising:
 a first step of driving a backlight unit using a first dimming value; and 
 a second step of driving the backlight unit using a second dimming value higher than the first dimming value, 
 wherein the first step and the second step are alternately repeated and 
 wherein a repetition number of the second step within one period of a driving frequency is set to satisfy a condition of “{(60/f)−1}”, where f is a natural number lower than 60, and 
 wherein the first step further comprises writing an image data, and the second step further comprises skipping an input image. 
 
     
     
       2. The dimming control method of  claim 1 , wherein the first step comprises:
 a ( 1 - 1 ) step of driving the backlight unit with the first dimming value from a start point of one period to a start point of a first second step; and 
 a ( 1 - 2 ) step of driving the backlight unit with the first dimming value at each time between the second steps, 
 wherein the ( 1 - 2 ) steps are performed during the same period. 
 
     
     
       3. The dimming control method of  claim 2 , wherein the second step comprises:
 a ( 2 - 1 ) step of controlling the backlight unit with the second dimming value immediately after the ( 1 - 1 ) step; and 
 a ( 2 - 2 ) step of controlling the backlight unit with the second dimming value after a first ( 1 - 2 ) step, 
 wherein a period of the ( 2 - 1 ) step is set to 75% to 90% of a period of the ( 2 - 2 ) step. 
 
     
     
       4. The dimming control method of  claim 2 , wherein the second step comprises:
 a ( 2 - 1 ) step of controlling the backlight unit with a ( 2 - 1 ) dimming value immediately after the ( 1 - 1 ) step; and 
 a ( 2 - 2 ) step of controlling the backlight unit with a ( 2 - 2 ) dimming value greater than the ( 2 - 1 ) dimming value after the first ( 1 - 2 ) step, 
 wherein the ( 2 - 1 ) step and the ( 2 - 2 ) step are set to have the same period, and the ( 2 - 1 ) dimming value is set to be greater than the first dimming value and smaller than the ( 2 - 2 ) dimming value. 
 
     
     
       5. The dimming control method of  claim 1 , wherein a sum of the period in which the first step is performed and the period in which the ( 1 - 2 ) step is performed is within a range of 1/240 seconds to 1/60 seconds. 
     
     
       6. A liquid crystal display (LCD) device comprising:
 a backlight unit irradiating light; 
 a display panel that displays a gray level to control a transmission amount of light irradiated from the backlight unit; 
 a timing controller that generates a timing control signal to drive the display panel based on first to (60/f) fields as one period at a frame frequency of 60 Hz or lower; 
 a driving circuit unit that drives the display panel in response to the timing control signal; 
 a dimming controller that generates first pulse width modulation (PWM) signals during a first field, and alternately outputs the second PWM signal and the first PWM signal during a second field; and 
 a light source driver that drives the backlight unit by a first dimming value in response to the first PWM signal and drives the backlight unit by a second dimming value set to have a duty ratio higher than that of the first dimming value in response to the second PWM signal, 
 wherein the dimming controller outputs the second PWM signal “{(60/f)−1}” times within one period of the frame frequency, wherein f is a natural number lower than 60, and 
 wherein the timing controller writes an image data during the first field and skips an input image during a second field to the (60/f) field. 
 
     
     
       7. The LCD device of  claim 6 , wherein the dimming controller sets a period in which the second PWM signal is output in the second field, to be longer than a period in which the second PWM signal is output in a third field. 
     
     
       8. The LCD device of  claim 6 , wherein the dimming controller alternately outputs a third PWM signal and the first PWM signal in a third field, and sets a duty ratio of the third PWM signal to be higher than a duty ratio of the second PWM signal. 
     
     
       9. The LCD device of  claim 6 , wherein the second dimming value set to have a value great enough for the user to recognize a difference between brightness when the backlight unit is driven using the first dimming value and brightness when the backlight unit is driven using the second dimming value. 
     
     
       10. The LCD device of  claim 6 , wherein the dimming controller drives the backlight unit using the first dimming value in the first field, and drives the backlight unit using a second dimming value and the first dimming value in the second field to nth field. 
     
     
       11. A dimming control method of a liquid crystal display (LCD) device comprising:
 driving a backlight unit using a first dimming value during a first field, 
 writing an image data during the first field, 
 driving the backlight unit using a second dimming value higher than the first dimming value during a first duration of a second field, 
 driving the backlight unit using the first dimming value during a second duration of the second field, and 
 skipping an input image during the second field. 
 
     
     
       12. A liquid crystal display (LCD) device comprising:
 a backlight unit irradiating light; 
 a display panel that displays a gray level to control a transmission amount of light irradiated from the backlight unit; 
 a timing controller that generates a timing control signal to drive the display panel based on first to (60/f) fields as one period; 
 a driving circuit unit that drives the display panel in response to the timing control signal; 
 a dimming controller that generates first pulse width modulation (PWM) signals during a first field, and alternately outputs the second PWM signal and the first PWM signal during a second field; and 
 a light source driver that drives the backlight unit by a first dimming value in response to the first PWM signal and drives the backlight unit by a second dimming value set to have a duty ratio higher than that of the first dimming value in response to the second PWM signal, and 
 wherein the timing controller writes an image data during the first field and skips an input image during a second field.